Currently, usually a compound system of brominated epoxy resin and dicyandiamide, or a compound system of multifunctional epoxy resin and phenolic aldehyde, is used as the base material for making a PCB. The former has good adhesiveness and machinability, but comparatively bad heat resistance. So, with the lead-free times coming, the heat resistance of a copper cladded laminate is required to be improved. The IPC 4101B standard requires specifically about the four major indicators of a laminate, glass transition temperature (Tg), thermal degradation (TD), time to delamination T XXX, and Z-axis coefficient of thermal expansion (CTE). So, the compound system of multifunctional epoxy resin and phenolic resin is more and more popular in the industry of copper cladded laminate. By using phenolic resin as the hardener, heat resistance and humidity resistance of a copper cladded laminate are greatly improved. However, at the same time, the adhesiveness of the laminate becomes bad, and the machining cost is also obviously increased. So, it is also a good technique to introduce a thermoplastic material with good heat resistance into the matrix resin, and by the technique of interpenetrating polymer networks (IPN), the combination property of the epoxy resin compound is improved. Thermoplastic polyphenylene ether resin has excellent machinability, dielectric property, and a comparatively high glass transition temperature. The polyphenylene ether resin after being heated or after molecular weight redistribution can be compatible with epoxy resin, and with other ingredients, the polyphenylene ether resin can react with epoxy resin by heat cured cross-linked reaction, so as to prepare a copper cladded laminate with excellent heat resistance and dielectric property.
As detailedly reported in the literature [1], dissolve PPO resin into toluene solvent, then respectively add 1%-2% BPA chain-cutting agent, TMDQ, benzoyl peroxide, etc. as the initiator agents, and then react at 90° C. for 2 hours, so as to get low molecular polyphenylene ether resin. After that, add a certain amount of novolac epoxy resin, “Upstage” resin, phenolic resin, zinc stearate, titanate, etc. as the ingredients, stir for 15 minutes, thereby obtaining a glue solution, then impregnate a fiberglass cloth with the glue solution, then bake and cure the impregnated fiberglass by heating and pressing at a certain condition, so as to prepare a copper cladded laminate with good heat resistance. Wherein, the preparation method of “Upstage” resin is that: use 50 parts by weight of 828 epoxy resin, 30 parts by weight of tetrabromobisphenol A, 20 parts by weight of novolac epoxy resin, and 0.2 parts by weight of catalyst to react at 165° C. for 2 hours; wherein, the catalyst to be used can be tetraethylammonium, 2-aminopyrimidine, or triphenylphosphine, etc. The novelty of the literature is the preparation of “Upstage” resin. Although the method can solve the compatibility and heat resistance of PPO and epoxy resin, it still has two disadvantages. First, the DMA map of the final laminate has two peaks, which means the compatibility of PPO and epoxy resin is not good enough. Second, the preparation process is too complicated, which needs two times of reaction, and the reaction temperature is too high, thereby being not good for batch production.
As reported in Chinese patent with the publication number CN1194038, polyphenylene ether resin with the molecular weight being 10000-30000 is heated and dissolved together with phenolic compounds or novolac, then peroxides of certain structure and catalyst are added in for redistribution reaction, thereby obtaining polyphenylene ether resin with the molecular weight being 1000-4000. The emphasis of the patent is the selected peroxides of certain structure, of which the decomposition product is alcohols with a comparatively low boiling point (lower than 150° C.), and the selected peroxides can be:

The copper cladded laminate prepared via the above mentioned reaction has excellent combination property. However, since the selected peroxides have comparatively low activity, the chain scission reaction can only occur as adding a certain amount of catalyst or being at a special condition.
Dr. Chunshan Wang respectively used phenolic aldehyde, dicyclopentadiene phenolic aldehyde, DOPO phenolic aldehyde, etc. as the chain-cutting agent to react with polyphenylene ether at a certain condition, thereby preparing a series of polyphenylene ether resins of a different structure. Then the prepared polyphenylene ether resin is curing with epoxy resin, amine type hardener, imidazole catalyst, etc. at a certain temperature, and the basic property of the cured resin is tested. Wherein, the principle of the reaction of dicyclopentadiene and polyphenylene ether is as the following:

However, the cured resin prepared via the above mentioned method generally has a comparatively high Df value, which is not good for the signal transmission of a high-frequency PCB.